In an electrochemical fuel cell, uniting a generator part and a frame part as one body by a hot-press method is proposed, as a sealing method which seals a path shaped by an electrolyte membrane and a separator for a fuel gas containing hydrogen or an oxidative gas containing oxygen. Two electrodes sandwich the electrolyte membrane in the generator part, and an opening area of the frame is marginally smaller than one of the generator parts made of plastic. One of these examples is disclosed in Japanese Laid-Open Patent Application No. 10-199551. Moreover, in the above-mentioned method, the path shaped by the electrolyte membrane and the separator for the fuel gas or the oxidative gas is sealed by providing a seal such as an O-ring between the frame part and the separator.
As another method, a method in which the generator part and the separator are connected by using adhesives is also proposed. In this method, the adhesives function as a comparatively soft seal after the connection, and the adhesives seal the path for the fuel gas or the oxidative gas.
In the aforementioned methods, which unite the generator part and the frame part as one body and furthermore puts the seal between the frame and the separator, sealing ability on the sealing surface could not be secured, because a clearance between the frame and the separator varies by a thermal expansion caused by heat of the electrolyte membrane in the generator part.
Furthermore, in the above-mentioned method which uses the adhesives, when a fuel cell stack is assembled by stacking a plurality of the generators and the separators, a stiffness of the fuel cell stack is weakened by laminating sealing parts using adhesives. Consequently, the fuel cell stack can not have sufficient stiffness and rigidity.